Rosacea May Have a Bacterial Cause

Joe Barber Jr, PhD

August 30, 2012

August 30, 2012 — Accumulating evidence suggests that rosacea is a bacterial disease caused by the overproliferation of Demodex mites in the skin, according to the findings of a literature review by Stanishaw Jarmuda, BS, from the University of Medical Sciences in Poznan, Poland, and colleagues. They presented their findings in an article published online August 29 in the Journal of Medical Microbiology.

The authors note that research efforts have been devoted toward elucidating a potential microbial cause of rosacea. "Over a significant period of time there have been numerous attempts to connect the etiopathogenesis of rosacea with the presence of some microorganisms on or within the skin including Demodex mites and bacteria," the authors write "It is well established that there is a higher density of Demodex mites in the skin of rosacea patients than controls but the significance of this has been disputed."

Although Demodex colonization is common in humans, rosacea occurs at a much lower prevalence. The authors note that several studies suggest that Demodex may become pathogenic in the context of immunosuppression, which would allow Demodex to grow uncontrollably.

In line with this hypothesis, data indicate that patients with rosacea have an average Demodex density of 10.8 mites/cm2 compared with 0.7 mites/cm2 in healthy people. Moreover, in another study of patients with papulopustular rosacea, Demodex folliculorum was detected in the follicle secretion of 90.2% of affected patients, but only 11.9% of control patients.

The authors also noted that a hypothesis regarding the role of Demodex mites in the pathogenesis of rosacea is that these mites serve as vectors for the causative microorganisms. Bacillus oleronius was isolated from a Demodex mite obtained from a patient with rosacea, and this bacterium was observed to invoke an immune reaction in 73% of patients with papulopustular rosacea, compared with only 29% of control patients.

In addition, in a previous study, Staphylococcus epidermidis was isolated from the pustules of 9 of 15 patients with papulopustular rosacea, but the bacterium was not present on unaffected areas in the same patients. Other research revealed that this bacterium was susceptible to antibiotics that are commonly used in the treatment of rosacea.

The authors noted that despite these findings, the role of Demodex mites and their associated bacteria in the pathogenesis of rosacea remains unresolved. "The lack of immunological response to Demodex mites in healthy skin raises the possibility of localized immunosuppression facilitating the survival of the mite," the authors write. "Hopefully, the results of further research will bring us closer to understanding the role of microbes in the pathogenesis of rosacea and assist in the development of new and more effective therapies for the treatment of this disfiguring disease."

The authors have disclosed no relevant financial relationships.

J Med Microbiol. Published online August 29, 2012. Full text